[ylinwind]

Description

An icon-only Tab (Tab::new().icon(..)) collapses to the width of its icon, so the icons of a segmented TabBar pack against each other and the selected segment's raised fill hugs the glyph with no inset.

The icon branch sizes its content box with w(inner_height * 1.25), but the same box also carries flex_1(). That zeroes the flex basis and allows shrinking, so the tab resolves to the icon's own width plus borders: a medium TabVariant::Tab icon tab measured 18px instead of 37.5px. The fix adds a matching min_w, so the box keeps the width it asks for while flex_1() tabs can still grow to fill the bar (#3032 is unaffected).

Regression

This worked until v0.8.1. Bisecting 288767cc..ae6a3fd with the new test lands on 99576db (Bump v0.8.1), which upgrades GPUI from gpui-pre 0.3.9 to 0.3.10 and with it taffy to 0.15. The tab code itself did not change there; the newer layout no longer keeps the w(..) width of a flex_1() box when its parent is sized by content, so the explicit min_w is now needed.

Screenshot

Found in an account menu that uses TabBar::new(..).segmented().small() with three icon tabs (Monitor / Sun / Moon).

Before	After
Each segment is ~16px at small size; the icons touch and the selected fill is as wide as the glyph	Each segment is 22.5px (small) as designed; icons are evenly spaced and the selected fill has its inset

Impact

• Only tabs built with Tab::icon change; labelled tabs, prefix/suffix tabs and Folder tabs go through the other branch and are untouched.
• Every variant is affected the same way: icon-only tabs grow from icon width to the designed inner_height * 1.25 content width (e.g. Segmented small 22.5px, medium 30px). A TabBar holding icon tabs becomes correspondingly wider; callers that relied on the collapsed width will see the bar grow.
• Within this repository no component uses icon-only tabs (dock and story icons are Buttons), so no in-repo layout changes.
• No event, focus or accessibility change; max_width still exempts icon-only tabs.

How to Test

• cargo test -p gpui-component --features test-support --lib tab:: — adds icon_only_tabs_keep_their_width, which checks every variant; it fails before the fix (Tab: icon-only tab is 18px, narrower than its 37.5px content) and passes after.
• Verified in a downstream app (Allsum account menu, segmented small icon tabs) in light and dark themes.

Checklist

• I have read the CONTRIBUTING document and followed the guidelines.
• Reviewed the changes in this PR and confirmed AI generated code (If any) is accurate. The fix and test were written with Claude Code.
• Passed cargo run for story tests related to the changes.
• Tested macOS, Windows and Linux platforms performance (if the change is platform-specific)

🤖 Generated with Claude Code